Design of a Microstrip Diplexer-Integrated Filtering Power Divider

This study proposed a new method and structure for designing a diplexer-integrated filtering power divider. A filtering function with equal power division was integrated with a diplexer. The multifunctional diplexer comprised eight coupled resonators and two 50-Ω resistors with a distributed coupling structure. Moreover, a connected coupling technique provided improved flexibility and freedom to construct the diplexer. High isolation was obtained using the proposed coupling configuration through the introduction of out-of-phase cancellation between multiple coupling routes. Moreover, because the distributed coupling structure was employed as an input, no complex matching network was required; this significantly reduced the size and simplified the design of the diplexer. Moreover, each channel passband was individually designed. For demonstration, a multifunctional diplexer operating at 1 and 1.15 GHz with a second-order Chebyshev bandpass response and equal power splitting was designed and fabricated using microstrip technology, and the simulation results were consistent with the measured results.